This invention is an improvement of present developed techniques for tertiary treatment of sewage waters by means of infiltration—percolation in permeable layers, as well as for cultivation of agricultural, sports and leisure areas by means of underground drip-feeders.
State of the art water treatment systems comprise devices for the surface supply of liquid to the layers (essentially flow and sprinkling) without complementary use of the layer surface to provide green tracts of flora. In contrast to the state of the art relative to the irrigation of green tracts by means of underground drip-feeders, the present invention incorporates the complementary use of the same as a treatment for sewage waters, thus recovering the major part of the water used.
The technique used in so called “green filters” is characterized by the use of superficial supply devices and the use of the same ground as a natural depuration system, without directly recovering the treated water and using the irrigated surface as a green area for profitable purposes.
In a prior art document, Spanish Patent No. 2,050,909, a procedure for treatment of sewage waters and polluted gases emanating from a hothouse is shown, for which it is necessary to cover the surface of what is termed an “earth layer reactor” by means of a structure of transparent roof and walls, so that toxic gasses rising from the bottom of the reactor can be recovered by this structure. In contrast, in the instant invention flora established over the layer surface of the treated area do not need to be covered inasmuch as they are grown in an entirely healthy environment (without gases, aerosols, odor or mud) and therefore are fully compatible with human activities whether for agricultural purposes or for sports, leisure or environmental activities which are totally unviable according to Spanish Patent No. 2,050,909.
Therefore, the “Photosynthetic harvest” described in Spanish Patent 2,050,909 fails to disclose a productive character and its field of plants serves only to improve the aesthetic and treatment of sewage waters; being useful only a very small varieties of vegetable species, which is contrary to the present invention wherein an extensive list of flora can be established that have an essentially economical role, increasing considerably the value of the depurated surface.
Finally in Spanish Patent No. 2,050,909, cultivation occurs directly over the same infiltration layer, whereas with the present invention, the flora is provided over a special substratum, independent of the same treatment system or infiltration layer and moisture rises by capillarity action from the drip-feeder net that supplies the referred layer.
Considering International Publication WO 9625366, this document describes an apparatus or device featured by two chambers. One is central and filled with a porous material, with different profiles and grain sizes, making a current of sewage water ascending from the base until its surface passes through the chamber, completely flooding such chamber that functions as a biological reactor. Water flowing through this first chamber falls, due to gravity into a second chamber surrounding the first chamber that is provided with several containers or lateral pots in which it is possible to cultivate plants. The fundamental differences of such prior art disclosures in respect of the present invention, are that, in the first one the treatment is made by means of a double chamber apparatus and not over the same surface. Sewage water is applied to the inside of the first chamber by means of an underwater flood system and anaerobic conditions dominate (absence of air in the deputation) which conditions the treatment in a different manner from the one in the present invention. Another main difference is to be noted in relation with the flora produced, as in International Publication WO 9625366 the flora occurs over the walls of an apparatus to contribute to the deputation and also the beautifying of said apparatus but not over the ground. This limits the type of flora, as well as the activities and the profitability of the system in a manner which are significantly different to those of the present invention.
Finally attention is invited to European Patent 0586805 in which a watertight compartment full of filtrating sand to which sewage water is supplied in a similar way as that described above, whereby a flood and layer saturation is provided that provides water to plants over the surface. The sewage water is supplied to the plant layer by means which are different from the underground drip-feeder used in the present invention. Furthermore, the sandy layer flood causes internal flows and anaerobic conditions that result in a depuration which is completely different to the one which takes place on the present invention. Further, in European Patent 0586805 only water plants can be cultivated, creating an unhealthy area which is unsuitable for the activities and productive processes possible over the cultivation areas of the invention. In view of the above prior art, it is concluded that flora cultivation has an accessory character that focuses primarily on minimizing the environmental impacts of the flooded areas as well as for contributing to some sewage waters treatment process, but being incompatible with the type of green areas of cultivation developed according to the present invention.